A mobile device can recharge an internal battery by wirelessly coupling to a power converter that is connected to a power source. Collectively, the mobile device and power converter be referred to as a “wireless power system” that transfers power from the power source to the internal battery.
A conventional wireless power system includes a transmitter that magnetically couples to a receiver within the mobile device to deliver power by electromagnetic induction. However, the conventional wireless power system also introduces voltage noise to the mobile device—via capacitive coupling—during transferring power. Voltage noise can affect voltage-sensitive systems within the mobile device, such as capacitive user input systems, capacitive fingerprint systems, capacitive proximity sensors, and so on.
As a result, many conventional mobile devices disable or limit the operation of voltage-sensitive systems when receiving wirelessly-transferred power, introducing inconsistencies to the user experience of operating the mobile device. Other conventional mobile devices incorporate grounded shields that reduce voltage noise, but also reduce the efficiency of the wireless power system, thereby increasing battery charging time and cost.